The present invention relates to optical scanners and more specifically to a multiple depth of field optical scanner.
Optical scanners are well known for their usefulness in retail checkout and inventory control. Optical scanners generally employ a laser diode, the light from which is focused and collimated to produce a scanning beam. An optical transceiver directs the beam against a plurality of stationary mirrors, and collects the beam after it is reflected by a bar code label. A motor rotates the optical transceiver, and a detector receives the returning beam. The pattern produced by such a scanner is characterized by lines oriented at various angles to one another. An example of an optical scanner can be found in commonly assigned U.S. Pat. No. 4,971,410, entitled, "Scanning and Collection System for a Compact Laser", issued Nov. 20, 1990, to Wike, Jr. et al. This patent is hereby incorporated by reference.
Multiple depths of field are desirable to increase the range from the scanner at which a scanner can read a given size of bar in a label, but have been difficult to implement. Some designs have included reciprocally oscillating mirrors.
Therefore, it would be desirable to produce an optical scanner which produces multiple depths of field, but which does not include a reciprocating mirror.